Open a terminal in ubuntu(ctrl+alt+t) and type this commands:
sudo add-apt-repository ppa:langdalepl/gvfs-mtp
sudo apt-get update
Then, launch Software Updater (previously known as Update Manager) and install the available updates. Afther you pdate everything restart pc.
if you want to revert back before making any changes:
sudo ppa-purge ppa:langdalepl/gvfs-mtp
reference web site: